Laser analyzers are capable of determining the presence and/or concentration of components in a gas or liquid medium. Laser gas analyzers may use tunable diode laser absorption spectroscopy to measure the concentration of a high-temperature component, a component containing a corrosive gas, toxic gas, or the like. Such laser gas analyzers may operate by irradiating the component to be measured with light from a tunable diode laser with high component selectivity, in a non-contact manner, at high speed, and in real time without being subject to interference of other components.
Laser analyzers typically include a laser light source and a detector. The laser light source typically irradiates, for example, an atmosphere of a gas to be measured with measuring laser light. The detector detects the measuring laser light that has passed through the measuring space of the atmosphere of the gas to be measured. The laser gas analyzer measures an inherent light absorption spectrum of molecules, ranging from an infrared region to a near infrared region, by using a diode laser in which the emission wavelength spectral line width is extremely narrow. The molecule-inherent light absorption spectrum may correspond to molecule vibrations or rotation energy transitions. Inherent absorption spectra of many molecules including O2, NH3, H2O, CO, and CO2 are in the infrared to near infrared regions of the electromagnetic spectrum. The concentration of the target component may be calculated by determining the absorbed amount (absorbance) of light at a specific wavelength.
Laser gas analyzers may use a peak height method, 2f method, spectral area method or the like. For example, according to the peak height method, the concentration of a component to be measured is determined from the peak height of an absorption spectrum. In the 2f method, a wavelength signal for scanning is modulated to obtain a modulated waveform having a frequency twice the frequency of the wavelength signal. Then, the concentration of a component to be measured is determined based on a P-P (peak to peak) value of the modulated waveform. In the spectral area method, the absorption spectrum is measured while the emission wavelength of the laser is scanned to obtain the spectral area. The component concentrations may be calculated based on the spectral area. Unlike the other methods, the spectral area method may not be affected by variations of the pressure or coexisting gas components.